The present invention relates to generally a ship for carrying low temperature liquid such as a liquefied natural gas (LNG) carrier and more particularly a device for receiving liquid leaked from a liquid storage tank which is supported on the bottom of a ship's hold by means of storage tank supporting structures.
FIG. 1 shows in section, a LNG carrier. Within a ship's hull 1, a tank 3 which is surrounded with a heat insulating layer 2 is supported on a bottom 4 of a hold by tank supporting structures 5 and 6. If a crack 7 is produced through the wall of the tank 3, the low-temperature LNG leaks and the leaked liquid 8 flows down along the heat insulating layer 2. A liquid-tight layer may be provided, as a countermeasure therefor, along the heat insulating layer 2. However, the tank 3 is supported on the hold bottom 4 by the tank supporting structures 5 and 6 which are extended through the heat insulating layer 2 so that there do exist clearances or gaps between the members of each of the tank supporting structures 5 and 6 and the heat insulating layer 2 and the leaked liquid 7 flows down through such clearances or gaps and cools the structural steel members of the bottom 4. Because such structural steel members are cooled by the leaked liquid locally and at extremely low temperature, the strength of the ship is adversely affected. In order to overcome this problem, there has been proposed to use steel capable of withstanding extremely low temperatures or to provide another heat insulating layer over the bottom 4 for preventing the leaked low temperature liquid from contacting the hold bottom 4, but both schemes are very expensive or uneconomical.
The present invention was made to overcome the above problem and has for its object to prevent a bottom of a ship's hold from being cooled by a leaked liquid by providing a device which is simple in structure. According to the present invention, means for receiving the leaked liquid is disposed below a tank supporting structure and more specifically a horizontal-displacement preventive tank-supporting structure.
The present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.